Solid state image pickup device having a time pulse generator, and method for replacing signals from a switch

ABSTRACT

A solid state image pickup device being provided with a photoelectric converter portion being composed of a plurality of pixels disposed in a row, a charge transfer portion for transferring the charges generated in the photoelectric converter portion, and a charge/voltage converter portion for converting the charges transferred by the charge transfer portion into voltages, comprising; a timing pulse generator portion for generating at least more than one pulse signal from among the followings: a first pulse signal for driving the charge transfer portion, a second pulse signal for reading out the charges generated in the photoelectric converter portion, a third pulse signal for sweeping out the charges generated in the photoelectric converter portion and a fourth pulse signal for discharging the charges transferred to the charge/voltage converter portion, and a switch circuit for switching over at least one pulse signal out of the abovementioned pulse signals to a predetermined fixed potential or a floating level.

BACKGROUND OF THE INVENTION

The present invention relates to a solid state image pickup device inwhich the charges obtained in a photoelectric converter portion aretransferred to a charge/voltage converter portion by predetermineddriving pulses, and converted into required voltages to output.

In general, a solid state image pickup device is provided with a row ora plurality of rows of photoelectric converter portions and the chargesobtained there are transferred to a charge/voltage converter portion foroutputting a voltage signal thus obtained.

The charges are transferred using predetermined clock pulses. The clockpulses necessary for transferring the charges are listed as follows;

(1) A readout-gate-pulse from the photoelectric converter portion to aCCD (Charge Coupled Device) register, (2) A transfer pulse fortransferring the charges obtained in the photoelectric-converter portionto the charge/voltage converter portion, (3) A transfer pulse in thelast stage right before the charge/voltage converter portion, and (4) Areset pulse in the charge/voltage converter portion.

In a case, these clock pulses are supplied from an external apparatus,or in another case that only a certain kind of clock pulse is suppliedfrom an external apparatus and the other clock pulses necessary fortransferring the charges are generated by a timing generator and adriver inside the device.

However, in a solid state image pickup device as mentioned in the above,in a case where a user wants to drive the device at a different timingwithin the conditions allowed to use the solid state sensor device, orin another case where a user wants to use only a part of the pluralityof photoelectric converter portions, sometimes the revision of anexternal circuit is needed by supplying clock pulses thereto, or aninfluence of a signal supplied from an external apparatus may exert onthe clock pulses generated by an internal timing generator.

Besides, in the case where a user wants to use only a part of theplurality of photoelectric converter portions, the clock pulses from anexternal apparatus intended to supply only to a part of the portions canbe delivered to all pixels in the photoelectric converter portion, andin particular in a case where high speed transfer is needed, since theload capacity of the transfer pulses becomes as much as the loadcapacity for all CCD registers, a physical restriction can be produced.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a solid state imagepickup device for solving the abovementioned problem.

In order to achieve the object described in the above, according to anaspect of the present invention, there is provided a solid state imagepickup device being provided with a photoelectric converter portionbeing composed of a plurality of pixels disposed in a row, a chargetransfer portion for transferring the charges generated in thephotoelectric converter portion with predetermined driving pulses, and acharge/voltage converter portion for converting the charges transferredby the charge transfer portion into voltages, comprising; a timing pulsegenerator portion for generating at least more than one pulse signalfrom among the following pulse signals: a first pulse signal for drivingthe charge transfer portion, a second pulse signal for reading out thecharges generated in the photoelectric converter portion, a third pulsesignal for sweeping out the charges generated in the photoelectricconverter portion and a fourth pulse signal for discharging the chargestransferred to the charge/voltage converter portion, and a switchcircuit for switching over at least a pulse signal out of theabovementioned pulse signals to a predetermined fixed potential or afloating level, or vice versa.

According to another aspect of the present invention, there is provideda driving method for a solid state image pickup device being providedwith a photoelectric converter portion being composed of a plurality ofpixels disposed in a row, a charge transfer portion for transferring thecharges generated in the photoelectric converter portion and acharge/voltage converter portion for converting the charges transferredby the charge transfer portion into corresponding voltages, wherein in afirst mode, a first pulse signal for driving the charge transferportion, a second pulse signal for reading out the charges generated inthe photoelectric converter portion, a third pulse signal for sweepingout the charges generated in the photoelectric converter portion and afourth pulse signal for discharging the charges transferred to thecharge/voltage converter portion are supplied to the solid state imagepickup device, and in a second mode, at least one pulse signal out ofthe signal pulses, the first, the second, the third or the fourth, ischanged over to a predetermined fixed potential or a floating level.

According to a further aspect of the present invention, there isprovided a driving method for a solid state image pickup device beingprovided with a plurality of photoelectric converter portions beingcomposed of a plurality of pixels in a row, and a plurality of chargetransfer portions for transferring the charges generated in respectivepixels disposed in a row in the plurality of photoelectric converterportions with predetermined driving pulses, wherein in a first mode, thedriving pulses are supplied to all of the plurality of the chargetransfer portions, and in a second mode, the driving pulses to besupplied to at least one charge transfer portion out of the plurality ofcharge transfer portions are switched over to a predetermined fixedpotential or a floating level.

Consequently, a solid state image pickup device according to the presentinvention has effects as shown in the following. In a case where a userwants to drive the device with a timing different from the present oneusing ordinary driving pulses, the ordinary driving pulses can be easilyswitched over to a predetermined fixed potential or a floating levelwith a switch circuit, which makes it possible to operate the deviceaccurately at a different timing from the present one. Further, it ismade possible to suspend the operation of an unnecessary pulse signal,while making it possible to control the generation of noise whose pulsesignal overlaps on the output waveform.

Further, it is made possible to lower the power consumption insuspending the driver operation by fixing unnecessary pulse signals at apredetermined potential. Even in a case where only a part of theplurality of photoelectric converter portions are used, the pulsesignals to be used for the unused photoelectric converter portions aresuspended, so that the load capacity of the charge transfer portion canbe lowered, thereby making it possible to correspond to a high speedtransfer operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram for explaining a solid state image pickupdevice according to a first embodiment;

FIGS. 2A and 2B show the circuit diagrams for explaining a switchcircuit:

FIG. 3 shows a timing chart of input and output pulses in the switchcircuit;

FIG. 4 shows a block diagram for explaining the solid state image pickupdevice according to a second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, the preferred embodiments of a solid state imagepickup device according to the present invention will be explainedreferring to the drawings. FIG. 1 shows a block diagram for explainingthe solid state image pickup device according to the first embodiment.The solid state image pickup device is provided with a photoelectricconverter portion 1 being composed of a plurality of pixels disposed ina row, a CCD-analog-shift-register 2 serving as a charge transferportion, for transferring the charges generated in the photoelectricconverter portion 1 with predetermined driving pulses, Φ1 and Φ2, atiming pulse generator portion (not shown) for generating driving pulsesΦ1, Φ2, etc., and switch circuits SW1 and SW2 for switching the levelsof the driving pulses Φ1 and Φ2 to be supplied to theCCD-analog-shift-register 2.

The solid state image pickup device is supplied with, besides drivingpulses Φ1 and Φ2 a pulse signal ROG to be supplied to a readout-gate, apulse signal ΦLH to be supplied to the last stage 2 n of theCCD-analog-shift-register 2, a pulse signal ΦRS to be supplied to areset gate RG, and driving pulses Φ1′ and Φ2′, having period differentfrom that of the driving pulses Φ1 and Φ2. The round marks shown in thedrawings indicate terminals provided on a substrate.

In this place, switch circuits SW1 and SW2 will be explained. In thefollowing explanation, although a switch circuit SW1 is taken as anexample, a switch circuit SW2 has the same constitution as that of theswitch circuit SW1.

FIGS. 2A and 2B show circuit diagrams for explaining the switch circuit.FIG. 2A shows a switch circuit for selecting a Φin or a predeterminedpotential Vc, and FIG. 2B shows a switch circuit for selecting a Φin ora floating level.

In an example shown in FIG. 2A, the switch circuit SW1 is composed oftwo MOS transistors TrA and TrB and an inverter. FIG. 3 shows a timingchart showing the relation between the switch pulse (SW pulse) and theΦin or the Φout in the switch circuit.

In the switch circuit SW1 shown in FIG. 2A, when a SW pulse is at a Highlevel, the High level pulse is applied to the gate of the MOS transistorTrA as it is, and to the gate of the MOS transistor TrB, a Low levelpulse obtained by reversing the High level pulse in the inverter isapplied. As a result, the MOS transistor TrA becomes a closed state andthe MOS transistor TrB becomes an opened state, accordingly, Φin isoutput as it is as a Φout.

On the contrary, when a SW pulse is at a Low level, the Low level pulseis applied to the gate of the MOS transistor TrA as it is, and to thegate of the MOS transistor TrB, a High level pulse obtained by reversingthe Low level pulse in the inverter is applied. As a result, the MOStransistor TrA becomes an opened state and the MOS transistor TrBbecomes a closed state, accordingly, predetermined potential Vc to beapplied to the source of the transistor TrB is output as a Φout.

The switch circuit SW1 shown in FIG. 2B is composed of one MOStransistor Tr. In this switch circuit SW1, when a High level SW pulse isapplied to the gate of the MOS transistor Tr, the MOS transistor Trbecomes a closed state and a Φin is output as it is as a Φout. When aLow level SW pulse is applied to the gate of the MOS transistor Tr, theMOS transistor Tr becomes an opened state and the Φin is cut off and theΦout becomes a floating level.

It is made possible to select the driving pulses Φ1 and Φ2 apredetermined voltage or a floating level to be supplied to theCCD-analog-shift-register 2 by providing the switch circuits SW1 and SW2between the terminals of the driving pulses Φ1 and Φ2, and theCCD-analog-shift-register 2 as shown in FIG. 1.

In other words, when the transfer of the charges is performed using thedriving pulses Φ1 and Φ2, the switch circuits SW1 and SW2 are kept in aclosed state. Thereby, driving pulses Φ1 and Φ2 can be applied to theCCD-analog-shift-register 2.

In short, the charge accumulated in each pixel S in the photoelectricconverter portion 1 is transferred to the CCD-analog-shift-register 2 bythe pulse ROG applied to the readout-gate, and the charge is transferredsuccessively toward the left in the figure by the driving pulses Φ1 andΦ2.

When a pulse signal ΦLH is applied to the last stage 2 n, the chargestored in each pixel is sent to a floating diffusion FD serving as acharge/voltage converter portion, and the charge in each pixel isconverted into a voltage corresponding to the quantity of the chargestored therein. The converted voltage is output from the output terminalVout through an output amplifier. The charges sent to the floatingdiffusion FD are discharged to a reset drain RD by the application of apulse signal ΦRS to the reset gate RG.

In repeating the abovementioned operation, it is made possible totransfer the charge generated in each pixel and take out the outputvoltage corresponding to the quantity of the charge generated in eachpixel.

On the other hand, in a case where a user does not want to use the Φ1and Φ2 as driving pulses, the switch circuits SW1 and SW2 are kept in aopened state for a desired arbitrary period of time. Thereby, the outputof the switch circuit becomes a predetermined potential Vc or a floatinglevel as shown in FIGS. 2A and 2B, and for the desired period of time,the driving pulses Φ1′ and Φ2′ can be applied to theCCD-analog-shift-register 2.

In short, driving pulses Φ1′ and Φ2′ can be applied to theCCD-analog-shift-register 2 without being influenced by driving pulsesΦ1 and Φ2, and in the same way as the above case, it is possible toperform the transfer of the charge and obtain the output of thecorresponding voltage.

As described in the above, in the solid state image pickup deviceaccording to the first embodiment, the switching of the potential ofdriving pulses can be easily performed by switching the circuits SW1 andSW2, and further in a case where other driving pulses Φ1′ and Φ2′ areused, the influence exerted by the driving pulses Φ1 and Φ2 can beeliminated. In addition, any change in the constitution of the timingpulse generator portion (not shown) for generating the driving pulses Φ1and Φ2 is not needed, so that there is no need to design a new circuit.

In the first embodiment, an example has been explained, in which theswitch circuits SW1 and SW2 are provided on the lines of the drivingpulses Φ1 and Φ2, for switching over the driving pulses Φ1 and Φ2 to apredetermined potential Vc or a floating level, however, it is alsopossible to provide switch circuits on other pulse lines for switchingover the other driving pulses to the potential Vc or a floating level.

For example, when the switch circuits are provided on the line of thepulse ROG to be applied to the readout-gate, it becomes possible toperform readout at another timing. In the similar way, by providing theswitch circuits on the line of the pulse ΦLH, the charge transfer in thefloating diffusion FD can be performed at a yet another timing.

In the similar way, by providing the switch circuits on the line of thepulse ΦRS, the discharge of the charge can be performed at a stillfurther timing. When the switch circuits are provided on the line of asweeping-out-gate-pulse (shutter pulse), not shown in a drawing, thesweeping out of the charge can be performed at an additional timing.

Next, a second embodiment will be explained referring to FIG. 4. A solidstate image pickup device according to the second embodiment comprises aplurality of photoelectric converter portions 1 b, 1 g, 1 r and 1 w,each being composed of a plurality of pixels in a row, a plurality ofCCD-analog-shift-registers 2 b, 2 g, 2 rand 2 w, for transferring thecharges generated in respective photoelectric converter portions 1 b, 1g, 1 r and 1 w, timing pulse generator portions (not shown) forgenerating driving pulses Φ1 and Φ2, etc. and switch circuits SW1 andSW2, for switching the levels of the driving pulses Φ1 and Φ2.

The photoelectric converter portion 1 b is composed of a plurality ofpixels in a row Sb coated with blue filters (not shown) and obtains thecharges corresponding to the blue color. The photoelectric converterportion 1g is composed of a plurality of pixels in a row Sg coated withgreen filters (not shown) and obtains the charges corresponding to thegreen color. Further, the photoelectric converter portion 1 r iscomposed of a plurality of pixels in a row Sr coated with red filters(not shown) and obtains the charges corresponding to red color. Thephotoelectric converter portion 1 w is composed of a plurality of pixelsin a row with no color filter coated thereon and it transfers charges asa black and white sensor.

In the solid state image pickup device described as above, the line ofthe driving pulses Φ1 and Φ2 is branched to two lines: one is the lineto supply pulses to;the CCD-analog-shift-registers 2 b, 2 g and 2 r,corresponding to blue, green and red, and the other is the line tosupply pulses to the CCD-analog-shift-register 2 w corresponding to theblack and white sensor. The switch circuits SW1 and SW2 are providedonly on the line of the driving pulses Φ1 and Φ2 for supplying pulses tothe CCD-analog-shift-registers 2 b, 2 g and 2 r, corresponding blue,green and red respectively. The constitution of these switch circuitsSW1 and SW2 are identical to those explained in the first embodiment(refer to FIGS. 2A, 2B and 3.)

In a case where color sensors (photoelectric converter portions, 1 b, 1g and 1 r, corresponding to blue, green and red) of comparatively lowoperating frequency are used, (normally, the output frequency of blue,green or red is in the range of 1 MHz to 5 MHz.), the switch circuitsSW1 and SW2 are kept in a closed state. Thereby, the driving pulses Φ1and Φ2 are applied to all CCD-analog-shift-registers 2 b, 2 g, 2 r and 2w.

In short, in this case, the total load of all CCD-analog-shift-registers2 b, 2 g, 2 r and 2 w becomes the load capacity of the driving pulses,however, in the case of the transfer of the charges using color sensors,since the operating frequency of these is comparatively low as describedin the above, the shift registers are able to correspond well enough.

In other words, the charges accumulated in respective pixels Sb, Sg, Srand Sw in the photoelectric converter portions 1 b, 1 g, 1 r and 1 w,respectively, are transferred to the respectiveCCD-analog-shift-registers 2 b, 2 g, 2 r and 2 w by the ROG pulsesapplied to the readout-gate, and they are transferred successivelytoward the left in the drawing by the driving pulses Φ1 and Φ2.

When the pulse ΦLH is applied to the last stage 2 n, the chargegenerated in every pixel corresponding to every color is sent to thefloating diffusion FD serving as the charge/voltage converter portion,and each of them is converted into a voltage corresponding to thequantity of the charge. These voltages are output from output terminals,Vout-B, Vout-G, Vout-R and Vout-w, through respective output amplifiers.The charges sent to the floating diffusion FD are discharged to thereset drain RD by the application of a pulse ΦRS to the reset gate RG.When the output for a color picture is to be obtained, the signalcorresponding to black and white output from the output terminal Vout-wis not used.

By the repetition of the above operation, it is made possible totransfer the charge generated in each pixel and take out the outputvoltage corresponding to each color.

On the other hand, when the black and white sensor (photoelectricconverter portion 1 w) is used aiming at high speed transfer (normallyequal to or higher than 5 MHz), the switch circuits SW1 and SW2 are keptin a opened state. Thereby, the driving pulses Φ1 and Φ2 are not appliedto the CCD-analog-shift-registers 2 b, 2 g and 2 rcorresponding to colorsensors, and the voltage to be applied to it becomes a predeterminedvoltage Vc (refer to FIG. 2.) or a floating level, and the drivingpulses Φ1 and Φ2 are applied only to the CCD-analog-shift-register 2 w.

In short, in this case, only the load of the CCD-analog-shift-register 2w corresponding to black and white becomes the load capacity of thedriving pulses, so that the shift register is able to correspond wellenough to the transfer of the charges for black and white aiming at thehigh speed transfer.

In other words, the charges accumulated in respective pixels Sb, Sg, Srand Sw in the photoelectric converter portions 1 b, 1 g, 1 r and 1w aretransferred to the CCD-analog-shift--registers 2 b, 2 g, 2 r and 2 w,respectively, by the pulse ROG applied to the readout-gates. However,only the charges transferred to the CCD-analog-shift-register 2 w, towhich the driving pulses Φ1 and Φ2 are applied, are transferredsuccessively toward the left in the drawing.

When the pulse ΦLH is applied to the last stage 2 n, the charge in everypixel corresponding to black and white is transferred to the floatingdiffusion FD, serving as a charge/voltage converter portion, and thecharge is converted into a voltage corresponding to the quantity of thecharge of black and white by the floating diffusion FD. The voltage isoutput from the output terminal Vout-w through an output amplifier. Thecharges sent to the floating diffusion FD are discharged to the resetdrain RD by the application of a pulse ΦRS to the reset gate RG.

In repeating the operation mentioned in the above, the charge generatedin every pixel corresponding to black and white can be transferred tothe CCD-analog-shift-register 2 w and the output voltage can be takenout from it. In short, a signal corresponding to black and white can beobtained at a high speed.

In the abovementioned second embodiment, a device being provided withfour photoelectric converter portions 1 b, 1 g, 1 r and 1 w, and fourCCD-analog-shift-registers 2 b, 2 g, 2 r and 2 w each corresponding toblue, green, red and white was explained, however, the present inventionis not limited to the above, and the invention can be applied to adevice being provided with other number of photoelectric converterportions.

For example, in a case where a user wants to obtain a color picture witha device being provided with three photoelectronic converter portionsand CCD-analog-shift-registers corresponding to blue, green, and red,driving pulses are supplied to all these CCD-analog-shift-registers, andwhen he/she wants to obtain a black and white picture, for example, aswitch circuit is so constituted that the driving pulses are suppliedonly to a CCD-analog-shift-register corresponding to, for example,green. Thereby, with a device being provided with only color sensors, acolor picture can be naturally obtained and also pictures of black andwhite can be obtained at a high speed.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

1-3. (canceled)
 4. A solid state image pickup device provided with aphotoelectric converter portion having a plurality of pixels disposed ina row, a charge transfer portion for transferring the charges generatedin said photoelectric converter portion, a charge/voltage converterportion for converting the charges transferred by said charge transferportion into voltages comprising: a transfer register; circuitryoperable to selectively apply to the transfer register one of a groupcomprised of a first pulse signal, a fixed voltage level, and a floatlevel; and wherein said transfer register receives the floating levelwhen said transfer register is not in use.
 5. A method for driving theread-out of a solid state image pickup device provided with aphotoelectric converter portion having a plurality of pixels in a row, acharge transfer portion for transferring the charges generated in saidphotoelectric converter portion, a charge/voltage converter portion forconverting the charges transferred by said charge transfer portion intovoltages, wherein in a first mode, a first pulse signal for driving saidcharge transfer portion, a second pulse signal for reading out thecharges generated from said photoelectric converter portion to saidcharge transfer portion, a third pulse signal for sweeping out thecharges generated in said photoelectric converter portion, and a fourthpulse signal for discharging the charges transferred to saidcharge/voltage converter portion, are all selectively supplied to saidsolid state image pickup device, in a second mode, selectively replacingat least one of the first through fourth pulse signals with a floatinglevel and subsequently applying a different pulse signal to the sameinput at which said one pulse signal is replaced with the floating leveland wherein the register receives the floating level when the transferregister is not being used.
 6. A method for driving the read-out of asolid state image pickup device provided with a plurality ofphotoelectric converter portions arranged in a plurality of rows, eachrow composed of a plurality of pixels, and a plurality of chargetransfer portions for transferring the charges generated in respectiverows of pixels, wherein, a switch circuit selects between two modes,comprising: a first mode in which the switch circuit passes drive pulsesare generated by a pulse generator to the charge transfer portions, anda second mode in which the switch circuit replaces at least one of thedrive pulses with a floating level, and wherein a different drivingpulse is subsequently applied to the same input at which the drivingpulse is replaced with the floating level.
 7. A solid state image pickupdevice being provided with a plurality of photoelectric converterportions arranged in a plurality of rows, each row having a plurality ofpixels, a plurality of charge transfer portions for transferring thecharges generated in said photoelectric converter portions, and aplurality of charge/voltage converter portions for converting thecharges transferred by each charge transfer portion into voltages,further comprising: a first switch circuit operable to selectivelyconnect a first input of at least one of the transfer registers to oneof a group of signals comprised of: a first pulse signal, a fixedvoltage level, and a float level; and a second switch circuit operableto selectively connect a second input of at least one of the transferregisters to one of a group of signals comprised of: a second pulsesignal, a fixed voltage level, and a float level, wherein the transferregister receives a float level when not in use.
 8. A solid-state imagepick-up device comprising: a timing pulse generator; a signal transferdevice and switching circuitry connected between the timing pulsegenerator and the signal transfer device wherein the switching circuitryis operable to selectively connect an input of the signal transferdevice to one of a group comprised of: the timing pulse generator, afixed voltage level, and a floating level wherein the transfer registerreceives a float level when not in use.